Biomedical subjects

H Seo

Publications and source records attributed to H Seo.

At least 217 records · Page 12Linked to original sources

PubMed1991

Diuretics modify [Arg8]vasopressin-stimulated cAMP but not atrial natriuretic peptide-stimulated cGMP formation in renal cells.

The present study was undertaken to examine whether sulfonamide-derived diuretics affect [Arg8]vasopressin (AVP)-stimulated or atrial natriuretic peptide (ANP)-stimulated cyclic nucleotide formation in cells cultured from rat or dog kidney. In rat renal cells, all four sulfonamide-derived diuretics examined significantly suppressed 10(-9) M AVP-stimulated cAMP formation at concentrations of 10(-4) and 10(-3) M, while basal cAMP formation was unchanged by the diuretics. When cells were stimulated with 10(-7) M AVP, low ceiling diuretics (indapamide and trichlormethiazide) did not suppress cAMP formation, while high ceiling diuretics (furosemide and azosemide) significantly suppressed cAMP formation at concentrations of 10(-4) and 10(-3) M. The suppressive effect of the diuretics on AVP-stimulated cAMP formation in vitro paralleled the reported diuretic potency of the agents in vivo. In dog renal cells, all four diuretics significantly suppressed 10(-9) M AVP-stimulated cAMP formation at concentrations from 10(-6) to 10(-5) M, while these diuretics did not change basal cAMP levels. High ceiling diuretics suppressed 10(-7) M AVP-stimulated cAMP formation, whereas low ceiling diuretics did not. The difference in effective doses between rats and dogs seems to be consistent with the species difference observed in vivo. None of the diuretics affected basal levels of intracellular cGMP or ANP-stimulated cGMP formation in cultured rat renal cells. In addition to the inhibition of the Na/K/Cl co-transporter, it is suggested that most sulfonamide-derived diuretics act, at least in part, by inhibiting the actions of AVP.

Animals↗

PubMed1991

Developmental expression of the prolactin gene in the chicken.

Steady-state levels of prolactin (PRL) mRNA in the pituitary gland during embryonic development were determined by dot blot analyses to relate the changes with those of pituitary and plasma levels of PRL. Steady-state levels of the 1.38-kb mRNA encoding the PRL prohormone remained low until Day 18 of incubation, increased on Day 19 of incubation, and reached maximum levels on the day of hatch but decreased 1 day after hatch. Changes in both pituitary and plasma concentrations of PRL closely mimicked those changes in PRL mRNA levels. Subsequently, both the levels of the pituitary PRL mRNA and PRL remained unchanged whereas those of plasma PRL increased 7 days after hatch. The results indicate that a progressive expression of PRL gene in the pituitary gland occurs 1-2 days before the hatch and concomitant increases in plasma concentrations of prolactin may be associated with physiologic changes in pulmonary respiration and hatching.

Amniotic Fluid↗

PubMed1991

Telescience testbed in human space physiology.

The present telescience testbed study was conducted to evaluate the feasibility of physiological experimentation under restricted conditions such as during simulated weightlessness induced by using a water immersion facility, a reduced capacity of laboratory facilities, a delay and desynchronization of communication between investigator and operator, restrictions of different kinds of experiments practiced by only one operator following a limited time line and so on. The three day's experiments were carried out following the same protocols. The operators were changed every day, but was the same the first and the third day. The operators were both medical doctors but not all round experts in the physiological experimentation. The experimental objectives were: 1) ECG changes by changing water immersion levels, 2) blood pressure changes, 3) ultrasonic Echo-cardiographic changes, 4) laser Doppler skin blood flowmetry in a finger, 5) blood sampling to examine blood electrolytic and humoral changes. The effectiveness of the testbed experiment was assessed by evaluating the quality of the obtained data and estimating the friendliness of the operation of the telescience to investigators and operators.

Aerospace Medicine↗

PubMed1991

Application of Doppler color flow imaging to determine valve area in mitral stenosis.

This study was undertaken to examine whether Doppler color flow imaging could accurately estimate the valve area in mitral stenosis. Doppler color flow assessments were performed in both an in vitro model and in 30 patients with mitral stenosis undergoing cardiac catheterization. In the experimental Doppler study using a circuit model, color jet width correlated well with actual orifice diameter (r = 0.99). In the clinical Doppler study, the mitral valve orifice was assumed to be elliptic and the mitral valve area was calculated from the following equation: (pi/4) (a x b), where a = color jet width at the mitral valve orifice in the apical long-axis view (short diameter) and b = the width in the 90 degrees rotated view (long diameter). Mitral valve area was also determined by two-dimensional echocardiography and the pressure half-time method, and the results for all three noninvasive methods were compared with those obtained at cardiac catheterization. By Doppler color flow imaging, mitral valve area could be determined in all patients and there was a significant correlation between the Doppler jet and catheterization estimates of mitral valve area (r = 0.93). Valve area determined by two-dimensional echocardiography correlated well with catheterization measurements in 26 patients (r = 0.84). However, the area could not be determined in 4 (13%) of the 30 patients because of technical problems. Although there was a fair correlation between the valve area determined by the pressure half-time method and catheterization (r = 0.79), this method tended to overestimate valve area in patients with aortic regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1991

Dexamethasone-nonsuppressible cortisol in two cases with aldosterone-producing adenoma.

Forty-one patients with aldosterone-producing adenoma (APA) were subjected to a dexamethasone suppression test (DST) before surgery. Serum cortisol and urinary excretion of 17-hydroxycorticosteroids were suppressed by dexamethasone in 39 patients [DST(+)]. In two patients (cases A and B), they were not suppressed [DST(-)]. Clinical manifestations of the two DST(-) patients were similar to those of DST(+) patients. Hypertension, hypokalemia, high serum aldosterone levels, and suppressed PRA were found in all of the patients. The cut surfaces of the adenomas from all of the patients, including cases A and B, were golden yellow, which is typical of APA. However, atrophies of the adjacent normal tissues were evident exclusively in the two DST(-) patients. After removal of the affected adrenals, the serum cortisol level was suppressed by dexamethasone in one of the DST(-) patients (case B). These findings suggested autonomous cortisol production by APA. To evaluate whether cortisol could be produced from the adenoma tissue, the presence of several steroidogenic enzymes was studied by immunohistochemistry and mRNA analysis in the adenomas and the adjacent nonneoplastic adrenals from the 2 DST(-) and 5 DST(+) patients. Immunohistochemical analysis demonstrated that steroidogenic enzymes were expressed in APA tumor tissues from both DST(-) and DST(+) patients. In both groups, mRNAs coding steroidogenic enzymes were present not only in the nonneoplastic but also in the tumor tissues. Quantitative analysis of the mRNA levels revealed that in the adrenals from DST(+) patients, the mRNAs were more abundant in nonneoplastic tissue than in tumor tissue. However, in those from DST(-) cases, the mRNAs were much more abundant in the tumor tissues than in the nonneoplastic tissues. These results indicate that tumor cells of the two DST(-) patients autonomously synthesized not only aldosterone but also cortisol. The diameters of the tumors from the two DST(-) patients exceeded 3 cm, while those from other DST(+) patients were smaller. In patients with large APA, adrenal insufficiency should be anticipated upon removal of the tumor.

Adenoma↗

PubMed1991

Nucleotide deletion resulting in frameshift as a possible cause of complete thyroxine-binding globulin deficiency in six Japanese families.

Complete T4-binding globulin deficiency (TBG-CD) is inherited in an X-linked fashion. A nucleotide substitution has been shown to cause this hereditary condition in caucasians of French Canadian origin. Heterogeneity in molecular mechanisms for TBG-CD has also been reported. Genomic DNA from a Japanese male exhibiting TBG-CD was subjected to polymerase chain reaction, and the generated DNA fragments were sequenced. A single nucleotide deletion was found in the first base of the codon for amino acid 352 of the common-type TBG molecule. This mutation causes a frameshift in translation and premature termination. Compared with common-type TBG, the mutated polypeptide results in 1) 22 different amino acids on its carboxy-terminus, 2) a 22-amino acid truncation, and 3) the absence of a potential N-linked glycosylation site. These alterations may lead to profound changes in the secondary and tertiary structures of the molecule. To ascertain the presence of this nucleotide deletion in the genomic DNA of affected subjects, a mutated primer was designed which together with the nucleotide deletion produced a new endonuclease restriction site in the polymerase chain reaction fragment. Results revealed the presence of the mutation in genomic DNA of the subject, and his mother was shown to have both mutant and normal alleles. The same mutation was also detected in five other unrelated families carrying TBG-CD. This mutation may be frequent in Japanese subjects with TBG-CD.

Amino Acid Sequence↗

PubMed1991

Suckling stimulates the expression of vasoactive intestinal polypeptide gene in rats.

The effect of suckling on vasoactive intestinal polypeptide (VIP) gene expression in the hypothalami was studied during the postpartum period in rats. Female rats were divided into two groups immediately after delivery. In one group, a mother was housed with 8 pups, and in the other, without any pups. The former group was named S(+) and the latter S(-). On days 0, 3, 6, 9 and 12 after delivery, the mothers were killed by decapitation. Hypothalamic VIP mRNA was measured by RNA dot hybridization. Although the VIP mRNA level showed no significant change after delivery in the S(-) group, VIP mRNA in the S(+) group on days 6, 9 and 12 increased to 1.6, 3.5 and 2.1 times higher than the level observed on day 0, respectively. These results suggest that suckling induces the synthesis of VIP after 6 postpartum days.

Actins↗

PubMed1991

Expression of prolactin gene in incubating hens.

Steady-state levels of the 1.38-kb mRNA encoding the prolactin prohormone, measured by northern and dot blotting using a radioactive cDNA probe, rose 10-fold with concomitant increases in concentrations of prolactin in anterior pituitary and plasma from non-incubating to incubating stages in Gifujidori bantam hens. Daily injections of a low dose of thyrotrophin-releasing hormone (TRH, 0.25 micrograms/kg) for 4 days caused no changes in the concentrations of prolactin of the mRNA, but a high dose (2.5 micrograms/kg) of TRH did induce a significant increase in prolactin mRNA levels compared to saline controls. The results suggest that gene expression for prolactin increases substantially during the incubation period and TRH may contribute, at least in part, to the increase in transcription of prolactin mRNA for prolactin biosynthesis in Gifujidori bantam hens.

Animals↗

PubMed1991

Hyperbaric diuresis is associated with decreased antidiuretic hormone and increased atrial natriuretic polypeptide in humans.

When men are exposed to a hyperbaric environment, urine flow increases. In order to elucidate the mechanism of this hyperbaric diuresis, a dry saturation dive experiment was carried out. Five male subjects were exposed to a 16-21 ATA (atmospheric pressure absolute) helium-oxygen (He-O2) environment for 4 days. Five blood samples were obtained in the early morning (0600-0630 h): once at predive 1 ATA air, 3 times at 16-21 ATA He-O2, and once at postdive 1 ATA air. Eight-hour timed urine samples, 0600-1400 h, 1400-2200 h, and 2200-0600 h (night urine), were collected throughout the experimental period. Urine flow markedly increased by the exposure to hyperbaria in the presence of constant creatinine clearance. The increase was mostly attributable to the urine flow during 2200-0600 h. The secretion of antidiuretic hormone (ADH) was suppressed at daytime and night during the exposure. On the other hand, the secretion of atrial natriuretic polypeptide (ANP) increased solely at night during hyperbaria and correlated with the increases of both the nocturnal urine flow and the nocturnal urinary excretion of sodium. These results suggest that both suppressed ADH secretion and stimulated ANP secretion cause hyperbaric diuresis.

Adult↗

PubMed1991

Superinduction of cytotoxic interferon-beta in glioma cells.

The possibility for new interferon therapy was investigated using the effect of endogenous human interferon-beta (HuIFN-beta) on various culture cell lines. Cell lines were exposed to superinduction agents (poly I: poly C, cycloheximide, and actinomycin D) and the production of endogenous interferon analyzed. Quantitative determination of HuIFN-beta and messenger ribonucleic acid (mRNA) showed HuIFN-beta was induced in all of five glioma cell lines, one of two melanoma cell lines, and all of three lung carcinoma cell lines as well as fibroblasts. Northern blot analysis showed HuIFN-beta mRNA induced in glioma cells was identical to that from fibroblasts. Endogenous HuIFN-beta induced from glioma cells had a cytostatic or cytocidal effect against various human glioma cell lines, even those resistant to fibroblast-derived HuIFN-beta. These results show it may be possible to use the induction of excess endogenous cytotoxic HuIFN-beta in human glioma tissue itself.

Fibroblasts↗

PubMed1990

Growth inhibition of glioma cells transfected with the human beta-interferon gene by liposomes coupled with a monoclonal antibody.

A human beta-interferon (HuIFN-beta) gene inserted into a eukaryotic expression vector (pSV2IFN-beta) was entrapped in liposomes having positive charges on their surface. Liposome-mediated transfection of the gene into cultured glioma cells (U251-MG) resulted in the secretion of HuIFN-beta into the medium. The HuIFN-beta level in the culture medium of glioma cells reached 24 +/- 8 (mean +/- SD) IU/ml after 96 h of incubation, at which level the growth inhibitory effect on the cells was found to be greater than 40 times as compared with exogenously added HuIFN-beta. When the plasmid-containing liposomes were coupled with a monoclonal antibody (G-22 MCA) against glioma-associated antigen, the level of HuIFN-beta in the medium was 178 +/- 26 IU/ml, resulting in a 7-fold increase, and the growth inhibitory effect was further elevated. Since the addition of a monoclonal antibody against HuIFN-beta to the medium did not cause the cell growth to resume, the growth inhibitory effect on the cells seems to be ascribed to HuIFN-beta produced in the cells transfected with its gene. Accordingly, the specific delivery of the HuIFN-beta gene into glioma cells by the use of such liposomes might become a useful technique for gene therapy of malignant glioma.

Animals↗

PubMed1990

Radioimaging of human glioma xenografts with 123I labeled monoclonal antibody G-22 against glioma-associated antigen.

Monoclonal antibody (MCA) G-22 is directed against a human glioma-associated surface antigen. Its availability for the radioimmunodetection of human glioma was analyzed by utilizing the xenografts in athymic mice. Nude mice with subcutaneous grafts of U251-MG or U251-SP glioma received intravenous administration of 123I or 131I labeled F(ab')2 fragment or whole immunoglobulin. Results of radioimaging revealed that 123I-labeled antibody was better than the 131I-labeled. It was also noted that administration of 123I-labeled F(ab')2 fragment of G-22 MCA enabled the imaging of human glioma xenografts weighing 80-650 mg after 48 hours. When biodistribution of 123I MCA was compared between G-22 and control antibodies, the percentages of dose/g in tumors were 5.228-1.799 at 30 hours and 4.112-1.132 at 48 hours with G-22 and they were 4.164-1.248 and 0.314-0.142 with control. The tumor/blood ratio until 72 hours after injection was constantly above 1 with G-22 and less than 1 with control antibody. These results indicate the potential usefulness of G-22 MCA for the radioimmunodetection of human gliomas.

Animals↗

PubMed1990

Radioimmunoassay of glioma-associated antigen in cerebrospinal fluid and its usefulness for the diagnosis and monitoring of human glioma.

Quantitative determination of human glioma-associated antigen in cerebrospinal fluids (CSFs) obtained from 66 patients with a variety of neurological diseases was performed by solid-phase radioimmunoassay with a monoclonal antibody (G-22). In this system, the minimum detectable amount of the antigen in the CSF was 8 ng/ml. It was demonstrated that CSF diagnosis of glioblastoma might be possible in the case of small tumors with a diameter of less than 2 cm. CSFs obtained from all 18 patients with glioma were positive and the level varied from 11.2 to 186.1 ng/ml. The antigen level in the cystic fluid of the tumor was higher than that in CSF. There was a tendency for the antigen level in CSF to be correlated with the tumor size and the type of histology. The malignant types of glioblastoma or medulloblastoma showed higher levels than the benign type of ependymoma and astrocytoma. Most types of non-gliomatous brain tumor were negative except immature teratoma, meningioma with central neurofibromatosis, and metastatic brain tumor from lung cancer. We also noted that tumor progression or regression of malignant glioma could be predicted by the monitoring of the antigen in the CSF.

Adult↗

PubMed1990

Adrenocorticotropin increases expression of c-fos and beta-actin genes in the rat adrenals.

It is widely accepted that expression of protooncogenes is coupled with cellular proliferation and differentiation. Since ACTH stimulates not only steroidogenesis but also cellular proliferation, we investigated whether ACTH affects the expression of c-fos, c-myc, and beta-actin genes. The effect of ACTH on adrenal glands was studied in hypophysectomized rats. Changes in the mRNA levels were studied by Northern and dot blot analyses. It was demonstrated that ACTH induces increases in mRNAs encoding c-fos and beta-actin in adrenal glands of hypophysectomized rats. When stimulated by ACTH (5 IU/100 g BW), the mRNA levels of both genes increase rapidly; the maximum levels are observed at 30 min for c-fos and 6 h for beta-actin. Both mRNAs declined to near-control levels by 6-24 h. The levels of mRNAs encoding cholesterol side-chain cleavage cytochrome P-450 and 21-hydroxylase cytochrome P-450 began to increase 3 and 12 h after ACTH administration, respectively. This increase continued for 24 h after ACTH treatment. Increases in total adrenal RNA and adrenal weight occurred slowly after ACTH treatment. On the other hand, the levels of c-myc mRNA were very low and were not increased by ACTH administration. These results suggest that increased expression of c-fos and beta-actin genes by ACTH may have important roles in mediating its action on adrenals.

Actins↗

PubMed1990

Specific induction of fibronectin gene in rat liver by thyroid hormone.

The regulation of fibronectin (FN) gene expression by thyroid hormone was studied. Rats were rendered hypothyroid by thyroidectomy, and the administration of T4 or T3 was used to produce rats in various thyroid states. RNA was extracted from fresh liver, kidney, and heart, and FN mRNA was determined by dot blot hybridization with a 32P-labeled rat FN cDNA probe. The specificity of the hybridization was assessed by Northern blot analysis. In liver, thyroidectomy decreased the abundance of FN mRNA by half, and daily administration of physiological doses of T4 or T3 for 5-6 days restored FN mRNA to the control level. The administration of pharmacological doses of thyroid hormones induced a further increase in the abundance of FN mRNA. A significant dose-dependent correlation between serum levels of T4 and the abundance of FN mRNA was observed in liver. A receptor-saturating dose of T3 (200 micrograms) given to thyroidectomized rats produced a significant increase in FN mRNA within 6 h after injection, indicating that expression of the FN gene was induced relatively rapidly. Moreover, a nuclear run-off assay revealed that thyroid hormone induces expression of the FN gene at least in part at a transcriptional level. The amount of FN mRNA was also determined in kidney and heart of the same rats. Although the abundance of FN mRNA changed by thyroidectomy or the administration of thyroid hormone in those organs, the magnitude of changes were slight compared with those observed in liver. These results suggested that a marked and dose-dependent induction of the FN gene by thyroid hormone occurs specifically in liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Mechanisms of atrial natriuretic peptide (ANP) secretion by rat hearts perfused in vitro--Ca2(+)-dependent signal transduction for ANP release by mechanical stretch.

Effects of temperature, contraction frequency, and intraatrial pressure on immunoreactive ANP release were investigated in isolated rat hearts perfused in Langendorff or working mode. A reduction of temperature from 37 C to 27 degrees C caused a decrease of ANP release by 64% indicating its marked temperature-dependency (Q10 = 2.92). An increase of atrial contraction frequency from 300 to 500/min in Langendorff-perfused hearts did not cause a significant change in the ANP release. An elevation of left atrial filling pressure of working hearts from 8 to 18 and 28 cmH2O was associated with pressure-dependent, and reversible increase of the ANP release. This pressure-induced release of ANP was inhibited in a low calcium (50% Ca2+) medium or by nifedipine (10(-7) M). N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7, 10(-7)M), a potent calmodulin inhibitor, or ryanodine (10(-8)M) had similar inhibitory action against the pressure-induced increase of ANP release. These results indicate that ANP secretion is primarily regulated by mechanical stretch or distension of the atrial wall, while the atrial contraction frequency is less important as a physiological stimulus for the secretion. The stretch-induced ANP secretion may require an influx of calcium through the voltage-dependent Ca2+ channels. It was also suggested that Ca2+ release from the sarcoplasmic reticulum leading to an activation of calcium-calmodulin kinase may be included in the intracellular processes of ANP release by mechanical stretch.

Animals↗

PubMed1990

Age-related changes in growth hormone and prolactin messenger RNA levels in the rat.

Growth hormone (GH) secretion declines with age, while prolactin (PRL) secretion increases in rats. The age-related changes in the pituitary GH and PRL mRNA levels in the Wistar Tw rat were studied at 6, 12 and 18 months of age by cytoplasmic dot hybridization. Hormone and mRNA concentrations were expressed as values per micrograms GH-cell or PRL-cell DNA. Concurrent decrease in GH concentrations and GH mRNA concentrations with age was observed in female rats, but not in male rats. GH mRNA concentrations (per microgram GH-cell DNA) in male rats at 12 and 18 months of age were 88 and 66% of those at 6 months of age, but there was no difference. GH mRNA concentrations in female rats at 12 and 18 months of age were 51 and 53% of those at 6 months of age. A concurrent decrease in PRL concentrations and PRL mRNA concentrations was observed in both male and female rats. PRL mRNA concentrations (per microgram PRL-cell DNA) in male rats at 12 and 18 months of age were 37 and 18% of those at 6 months of age. PRL mRNA concentrations in female rats at 12 and 18 months of age were 51 and 31% of those at 6 months of age. Pituitaries in 12- and 18-month-old females contained more PRL and PRL mRNA than those at 6 months of age. These increases in PRL and PRL mRNA contents may result from the increase in the number of PRL cells, although each PRL cell had less PRL and PRL mRNA. These results suggest that the age-related changes in pituitary GH and PRL levels occurred at the transcription level of GH and PRL syntheses, and that the age-related changes in GH-cell and PRL-cell populations are responsible for the changes in GH and PRL secretions.

Aging↗

PubMed1990

Alteration in the expression of genes for cholesterol side-chain cleavage enzyme and 21-hydroxylase by hypophysectomy and ACTH administration in the rat adrenal.

The changes in steady-state levels of mRNA for cholesterol side-chain cleavage cytochrome P-450 (P-450scc) and steroid 21-hydroxylase cytochrome P-450 (P-450c21) caused by hypophysectomy and ACTH treatment were determined in rat adrenals. Hypophysectomy caused marked decreases in adrenal weight and total RNA per gland. Administration of ACTH resulted in increases in adrenal weight and total RNA. A significant correlation between the amount of RNA and adrenal weight was observed. Both P-450scc and P-450c21 mRNAs were decreased by hypophysectomy and increased by ACTH treatment. P-450scc mRNA decreased to 20% and P-450c21 mRNA to 76% of control values 1 day after hypophysectomy. ACTH caused a significant increase in P-450scc mRNA after 3 h. However, a significant increase in P-450c21 mRNA was observed 12 h after administration of ACTH. These results are concordant with previous studies in vitro utilizing cultured adrenocortical cells. Moreover, the induction of steady-state levels of P-450scc mRNA was faster than that observed by other investigators in studies in vitro. These results may indicate that integrity of the adrenal gland in vivo is important for the action of ACTH.

Adrenal Glands↗